A significant portion of established, conventional lighting systems that convert electrical energy to light using incandescent or fluorescent technologies. These two well-established technologies offer well known trade-offs. Many buildings and structures have existing (e.g., legacy) lighting systems. Some of these systems may have dimming systems installed that supply controllable electrical stimulation to lamp sockets, for example, so that adjustment of the electrical stimulation produces a corresponding adjustable light output level.
Two trade-offs between incandescent and fluorescent technologies may be found in their energy efficiency and dimmability. Their comparative strengths may be considered to arise out of the physics of their respective illumination mechanisms.
With regard to energy efficiency, incandescent lamps may be considered to dissipate significant heat energy in the process of emitting light. Incandescent lamps emit light by dissipating heat in a resistive filament, thus making that filament so hot that it glows. Much of the electrical energy supplied to an incandescent lamp is converted to (waste) heat rather than light. In contrast, a fluorescent lamp emits light when a sufficient voltage applied between electrodes excites a gaseous medium. In general, fluorescent lamps produce more light per unit of electrical input than a comparable incandescent. Specifically, fluorescent lamps may typically produce more visible spectrum lumens per watt than a comparable incandescent.
Another trade-off between these two technologies may be found in their dimmability. In terms of voltage and current, an incandescent lamp dims well. The light output is a generally smooth function of the electrical power dissipation in the incandescent filament. By smoothly controlling the electrical power input, the light output can be smoothly controlled over its entire operating range. In contrast, a fluorescent lamp may generally be considered a non-linear system, for example, because it may require a substantial voltage to excite the gases between electrodes at opposite ends of a tube. Because the impedance in the tube may change significantly during operation, smooth dimming of a fluorescent lamp generally calls for relatively large, complex ballast electronics in order to maintain the gas excitation and voltage conditions required to operate the lamp over a wide dynamic range.
More recently, LED lamp technology has started to become an attractive new alternative because it can offer higher energy efficiency than incandescent, and it can do so without the complex controls required to maintain gas excitation within a fluorescent lamp. Some LED lamps are starting to come on the market with the form factor of certain legacy incandescent lamps. However, retrofitting LED lamps into legacy incandescent dimming systems has presented some unexpected performance challenges that remain unresolved.